Watermelon is an important specialty crop that is common in all major agriculture production areas and accounts for 6.8% of the world area devoted to vegetable and melon crops (Derived from data supplied by United Nations Food and Agriculture Organization, FAOStat (http://faostat.fao.org/site/567/default.aspx). There were 8,900,300 of acres of watermelon grown in the world and 150,700 acres of watermelons grown in the United States in 2007. The United States is the fifth largest watermelon production country in the world. Asia is by far the most important watermelon production site with nearly ⅔ of the world area and slightly over ⅔ of the world production (United Nations, Food and Agriculture Organization, FAOStat (February 2008)). There were 125,550 acres of watermelon planted in the USA, accounting 7.25% of US vegetable acreage, with a total production of 39.551 million cwt and farm value of $492,446,000 in 2008 (USDA, NASS, Vegetables Annual Summary (2004-2008)). Majority of the watermelon acreage in the USA are seedless watermelon. California was the leading state in watermelon farm gate value, exceeded $72.981 million in 2004, due to higher percentage of triploid seedless watermelon grown in California. Seedless watermelon receives above the average price for seeded watermelons in the market. Triploid seedless watermelon also produces higher yields than the diploid seeded watermelons. The significantly increased watermelon productivity and farm value, as well as decreased production acreage, in the USA since the mid-1990s are the result of using triploid seedless watermelon varieties in commercial production.
The goal of plant breeding is to combine in a single variety or hybrid various desirable traits. Desirable traits may include resistance to diseases and insects, tolerance to heat and drought, reducing the time to crop maturity, greater yield, and better agronomic and produce quality. With mechanical harvesting of many crops, uniformity of plant characteristics such as germination and establishment, growth rate and maturity, are important. Other desired traits may include particular nutrient content, color, fruit shape, as well as taste characteristics.
As with many different plants, a watermelon plant contains a fruit part and a plant part. Each part contains different traits that are desired by consumers and/or growers, including such traits as flavor, texture, disease resistance, and appearance traits such as shape and color. The seedless trait in the watermelon fruit is highly desired by consumers. For production of seedless watermelon, optimum pollination characteristics of the pollenizer plant (plant provides viable pollen for the triploid plant) are desired.
Seedless watermelon plants are triploid and must be pollinated by the pollen of diploid watermelon plants. To provide adequate pollenization of seedless watermelon plants, it is current practice to plant diploid pollenizer plants over approximately 25-33% of the field surface. The remaining portion of the field is planted with the triploid plants. Thus, to maximize the value of the crop in the field, growers use high yield marketable diploid watermelon varieties, which ultimately compete with the triploid seedless varieties for sun, nutrients, and space. The present invention recognizes the need to increase the pollenizing capacity of diploid watermelon plants in order to decrease the ratio of diploid to triploid plants in the field, thereby increasing the yield of the seedless watermelon. The present invention further recognizes the need for phenotypic characteristics of the diploid pollenizer plants, which permit these diploids to be planted in close proximity to the triploid plants and to share the field surface with the triploid plants, thereby effectively decreasing the surface area of the field required for the diploid pollenizers of the invention. The present invention also further recognizes the need for pollenizer plants with improved resistance to diseases.